1. Field of the Invention
The present invention relates to new aniline derivatives, a process for the preparation thereof, new conducting polymers using them as monomers and processes for the preparation thereof for use in battery electrodes, electrochromic device materials, sensors and the like due to their excellent stability and outstanding electrochemical and electrochromic properties.
2. Description of the Prior Art
A number of conducting polymers are known in the art including polyacetylenes, polypyrroles, polythiophenes and polyanilines. In spite of their many good characteristics such as light weight, practically high conductivity, semiconductor properties, electrochromic properties and redox cyclability, the conductive polymers have rarely been commercialized due to drawbacks such as poor processibility, low redox cyclability and weak mechanical properties.
In order to find solutions to the above problems, a number of methods are disclosed as described in the following.
Firstly, there is a process for improving mechanical strength of conducting polymers by using p-toluene sulfonate as a dopant for an electrochemical preparation of polypyrrole instead of using conventional inorganic dopants such as lithium perchlorate and tetraethylammonium bromide (IBM J. Res. Rev., 1983, 27, 342). However, it was found that p-toluene sulfonate dopant dissolves out into the solution during the repetitive redox cycling of the conducting polymer in electrolytic solution.
Another example (Chem. Lett., 1986, 687) is using poly(styrene sulfonate) instead of p-toluene sulfonate as a dopant to prevent the dissolution problem, where the concentration of electroactive center in the conductive material is diluted resulting in lowering energy density of the rechargeable battery when used as an electrode.
Secondly, to improve mechanical strength of conducting polymers, a composite of conducting polymers was made with conventional polymers such as polyvinylchloride or polystyrene (J. Polym. Sci., Polym. Commun., 1985, 23, 1687). However, there still exists a need to improve the coulombic charge density because the concentration of electroactive center in the composite is diluted by the polymer used.
Thirdly, a method using an alkyl side-chain derivative of thiophene as a monomer is disclosed (Macromol., 1987, 20, 212). For instance, 3-octylthiophene is polymerized to produce poly(3-octylthiophene) that is not only fusible but also soluble in organic solvents such as chloroform. However, expensive monomer price and low redox cyclability prevent the commercial utilization of the polymer.
Another method is to introduce a sulfonyl group in the monomer structure as in the case of poly(3-(3'-thienyl)-1-propanesulfonic acid) which can be used as an intramolecular dopant, where fast redox kinetics and a good processibility are achieved. However, there still is a problem such that the monomer preparation needs several synthetic steps.
As shown in above examples, various problems such as the method of monomer preparation, processibility and the redox stability of the polymer should be solved to widen the application area of the conducting polymers.